Method of reducing telephonic disturbances.



0. B. BLAGKWBLL & G. A. ANDEREGG,

' METHOD OF REDUCING TELEPHONIO DISTURBANGES. APPLICATION FILED APR.1 1, 1912.

v tented June 10, 1913- Fig.2.

In Van/tors,

UNITE I sra'rns OTTO B. BLACKWELL, OF MAPLEVJOOD, NEW JERSEY, AND GUSTAVUS A. ANDEREGG, OF OAK PARK, ILLINOIS, ASSIGNORS TO AMERICAN TELEPHONE AND TELEGRAPH COMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

METHOD OF REDUCING TELEPHONIC DISTURBANQES.

Specification of Letters Patent.

Patented .nme'io, 1913.

Application filed April 11, 1912. Serial No. 690,158.

To allwizomiivnag conccm:

Be it lmown that we, O'r'ro B. Brno]:-

ELL and Gosravos A. Anonnnce, residing twisted pairs included in a cable, there is liable to occur a disturbance commonly termed cross-talk, this being chiefly caused by inequalities in the capacities of the conductors of one pair with relation to those of another pair. This is especially troublesome in phantom circuits, in which there may be cross-talk between the phantom and both of its sides or physical circuits and also between said side circuits. This invention contemplates a method of nullifying .or reducing such disturbances by efiecting a more perfect balance of the capacities.

In the accompanying drawings, in which the same characters of reference are applied to like parts in all figures, Figural illustrates successive sections of a four-conductor component or quad of a cable, these sections being connected through a testing apparatus indicated conventionally, and Fig. 2 is a diagram disclosing .the distribution of capacities between the elements of a phantom circuit contained in a cable.

Our invention will be explained in its application to a quad or portion of a cable adapted for use in forming a phantom circuit, the four conductors of which are twisted in pairs and these pairs being twisted together, each two-conductor pair furnishing a physical circuit, while these circuits taken with the conductors of each in pa rallcl 'give a third pair of conductive elements camsfituting the phantom circuit. In Fig.;1+-ofthe drawings are illustrated *e. sections A and B of the quad htterminate at a cable maI1-. hole,-sect L containing the physical pair P comp gag, the conductor-s11 and 12 and the physical pair'P. having conductors 13 as they in appear as condenser and 14, these together forming the phantom pair 11l2, 13-14; the section B has corresponding pairs P with. the conductors l112, and P with the conductors 13, together with the phantom pair 11' -12', 1a" 14.

The relation of the capacities which may cause cross-talk in the quad A is illustrated diagrammatically in Fig. 2, in which the 'ca-' pac ties between the conductors themselves I a, b, 0, (Z; while the capacities of the respective conductors to ground, or to the sheath and other conductors of the cable, are illustrated as condensers c, f, g, k. If these capacities were equal or distributed so as to balance one another, there would be no transfer of potential and no cross-talk from these sources, but the capacities of a commercial cable are not uniform and mutual disturbances result. T 7 .ese disturbances may be shown to be approximately proportional tolas between the side circuits;

2(a-5c+d) (c-f,i.

between the phantom and the side circuit P; and

3 and 3 being the respective unbalances in the. sections A and B. If the connections of the pairs P and P? were transposed, the

pairs P and 1 3 remaining as before, the unbalance will be The pairs PTP may also-be transposed.

or both pairs together, but the same totals X y-l-g/ or y-y will be produced. It there fore appears that by properly choosing the conductors which areconnected, according to the amounts and relative direction of unbalance, a minimum cross-talk will result.

In the same way the total unbalance of the phantom to either side is'the algebraic sum of the unbalances of the sections, and this may be adjusted by connecting the sections in accordance with the respective capacity values. By joining the pair in one section to one or the other of the pairs in the succeeding section the magnitude of the imbalances brought together may be controlled, and ywhetherthese add or subtractmay be determined by the connection of the respective conductors of one pair to one or the other of the conductors of the pair chosen in the other section. a

Three sources of cross-talk have been considered the side to side'unbalance and that of the. phantom to each of the sides. How ever, if the correction is made for any two F of these, the possible combinations for adjustin the unbalance will be exhausted, and

the third must be left uncorrected as far as the two particular sections are concerned. Buttheremaining unbalance may be provided for in joining succeeding sections.

The determination of the capacities may be byany usual or desired method and employing any convenient apparatus; the details of the measuring operations will there ford not be described We may tentatively connect the conductor groups of successive sections in various combinationsthrough av Y measuring apparatus as conventionally indic'ated by'the dotted square20 in Fig. 1,; thaf ends of the sections being secured to terinitials 21 and joined by; conductors 22' within the apparatus, these 'conductonsbemeasuring devices (not shown). We then:

ing provided with tape 23 leading to the determine the capacity unbalances for the total length of both'sections. The conductors upon the completion of the test are disconnected from the measuring apparatus and permanently spliced to give a minimum capacity unbalance and consequently the least crosennnauene elements or the-phanftom being considered. 3 Or the funbalances for all the conductor groups in the sections may be separately measured and recorded, an the preferable connections chosen from 'these results.

As an example of results which might'be found in practlce, assume the groups of con-, ductors to be first connected directly 11 to .11, 12 to 1 2, 13 to 13' and\14 to '14, andthe capacity relation between the phantom P,

- 1:" and P P? to its side I, P measured and the e foundtobe an unbalance of twenty nuc ease rnicro-microfarads. The connection drawside circuit P, P? is then transposedysoithat it is connected 11'; 12 and 12, 11?,"and an unbalance of forty micro-microfarads obtaincd. The relatiorixfioff thephantom to the other side P, P is l' tlicn teste the companion PalRP, P being restore Lto its first or direct connection, since this gave the bet-f ter balance, and the side now under test directlyconnected-dl, 13, and 14, 1 1; an unbalance of three hundred and thirty micromicrofarads results.

Uponftransposing the side P, P, so that brought to the same value by transposing the second side-13, 14' and 14, 13, but this would have iven a greater unbalance of .three hundre and thirty micro-microfarads between this side and the phantom. The

final transposition of the first pair P, 1

obviously increased the unbalance of this side ofithe phantom, but to a less extent than it decreasedthe unbalance between-the sides.

"We claim ,1 The method of neducing disturbances between groups of adjacent conductors which consists in'determining the difierences in capacities of the conductors of-one g-rou withrelation to those of another, and then' .socombining the capacities of the groups that they tend to balance.

2. The method of balancing successive groups of conductors, between the conductors of each of which groups are inequalities in the capacities, which consists in determining suh inequalitiesqand then so joining the conductors in successive groups that said inequalities tend to neutralize one another.

4 3. The? method of balancing successive groups of conductors which consists in connecting the groups to one another in various combinations, measuring the capacities between the conductors as thus joined, and permanently connecting the conductors to give the preferred relation between the capacities.

"4. The method of balancing a phantom circuit, between the elements of success ve sections of which there are inequalities in capacity, which consists in determining; the inequality of capacity between the s1de c1r-.

ouits of the phantom and between the side circuits and the phantom, and then so join ing such elements in-the successive sections as to produce a minimum total unbalance.

5, The method ofreducing disturbances between adjacent conductors arrangeci in successive groups which consists in deter-- mining the differences in capacities of the conductors of one group with relation to those of another group of the series, and then so combining the capacities of the successive groups that'they tend to balance.

In testimony whereof, I'have signed my name to this specification in the presence of March, 1912.

two subscribing Witnesses, this 14th ciay of 15 OTTO B. BLAOKWELL. Witnesses: a I

ROBERT S. Smm; FRANK'POWLL. v i Intestimony whereof, I have signed my name to this specification in the presence of two subscribing Witnesses, this 5th deybf April, 1912. GUSTAVUS A. ANDEREGG.

Witnesses:

ROY C. JONES, EVANS SHUFF.

Copies of this patent may be obtained for five cents each, by addressing the Gommi ssioner-of Patents, V

Washington, D. C. 

